1. Field of the Invention
The present invention relates to a method for the production of a lutein-fatty acid ester concentrate, more particularly a method of obtaining a lutein-fatty acid ester concentrate of high purity by purifying marigold oleoresin.
2. Description of the Prior Art
Lutein-fatty acid esters are a yellow-orange pigment contained in fruits such as oranges, peaches, papayas, prunes and mangos. Lutein-fatty acid esters are also present in many flowers and vegetables, particularly in petals of marigold flowers remarkably. Dried and ground marigold flowers have been used as animal feeds for a long time, and oleoresin which is obtained by extraction of marigold flowers with a solvent has also been widely used as food color in recent years in addition to the above-mentioned application.
The recent scientific researches have reported that lutein is associated with risk reduction for age-related macular degeneration (AMD) caused by oxidative damage to macular area of retina (Journal of the American Medical. Association, 272, 1413–1420, 1994: Investigative Ophthalmology & Visual Science, 38, 1802–1811, 1997, etc.), and that lutein is effective for prevention of arteriosclerosis, prevention of cataract or suppression of carcinogenesis and etc. (British Medical Journal, 305, 335–339, 1992: The American Journal of Clinical Nutrition, 70, 517–524, 1992: American Journal of Epidemiology, 149, 801–809, 1999, etc). As such the use of lutein as a health food and a dietary supplement is also expected.
Marigold oleoresin is obtained when dried and ground marigold flowers are extracted with a hydrocarbon solvent such as hexane and petroleum ether or with a chlorinated hydrocarbon solvent such as dichloromethane, and the solvent is removed from the extract. But the content of lutein-fatty acid ester as an ester contained in oleoresins produced by the largest producers of marigold extracts is low, usually 14 to 20% (cf. U.S. Pat. No. 6,191,293), and is about 30 to 35% even in a superior grade type which is partly sold for food.
Thus, there has been a demand for a lutein-fatty acid ester concentrate of high purity in order to obtain more vivid color tones when it is used as a food color and in order to improve the functional efficiency when it is used as a dietary supplement.
As to a method of obtaining a lutein-fatty acid ester concentrate of high purity, “Purification of Lutein-Fatty Acid Esters From Plant Materials” (U.S. Pat. No. 4,048,203) and “Trans-xanthophyll Ester Concentrates of Enhanced Purity and Methods of Making Same” (U.S. Pat. No. 6,191,293) have been disclosed.
The former describes a method which comprises precipitating lutein-fatty acid esters from oleoresin which is dissolved in hot alkanol containing not more than four carbon atoms by cooling the solution, removing alkanol wherefrom by filtration and drying the lutein-fatty acid ester under vacuum. However, the purity of the lutein-fatty acid ester concentrate obtained by this method is 51%, which cannot be considered a high purity.
The latter describes a method of obtaining a purified trans-xanthophyll ester by contacting coronals (or flowers) of marigold flowers with a hydrocarbon solvent, removing wherefrom plant residue after sufficient extraction, evaporating the extract to obtain oleoresin, admixing the resulting oleoresin with an alcohol at ambient temperature and removing the alcohol containing impurity and cis-xanthophyll ester from the mixture.
By this method, however, the purity of lutein-fatty acid ester in the resulting oleoresin varies widely depending on the quality of the raw material, i.e. coronals (or flowers) of marigold flowers, and therefore, the purity of lutein-fatty acid ester in a concentrate obtained by purifying the said oleoresin also varies widely. For this reason, control of the raw material is necessary to obtain a lutein-fatty acid ester concentrate of high purity by this method, and as such it is difficult to stably obtain a lutein-fatty acid ester concentrate of high purity when most of the commercially available oleoresins are used as a starting material.